Quantity which is calculated during post-p … Quantity which is calculated during post-processing by appropriate formulae (e.g. efficiency, mean value, full load hour, electricity generation costs, cumulative amount of energy). Key performance indicators (KPI) should be suitable to quantify differences between the scenarios. The definition of a KPI depends on the research topic. Usually it is necessary to define various KPIs.ly it is necessary to define various KPIs.